Last night, the "48 Hours" TV program featured Waco, the raid, and the results. Naturally, they skipped the original reason for the raid (was there a legitimate reason?) and claimed that the fire was set from inside. Nor did they give a good reason for the final attack.

The fire was set from the inside when the police burned down the house in South Central Los Angeles back in 1971 when they got word that the Symbionese Liberation Army had people hiding there, and maybe even Patty Hearst!
It was set from the inside because tear gas canisters emit a lot of heat when the active ingredients are released.